IBM R40 FFixedHW register?

I'm testing out my new cpu driver for FreeBSD and came across an interesting case in supporting Px states. They work great on several laptops but the R40 can't set Px states. I looked at the ASL and found that the control/status register pair is FFixedHW.

            Return (Package (0x02)
            {
                ResourceTemplate ()
                {
                    Register (FFixedHW, 0x40, 0x00, 0x0000000000000199)
                },

                ResourceTemplate ()
                {
                    Register (FFixedHW, 0x10, 0x00, 0x0000000000000198)
                }
            }

I guess I have to find the datasheet for that model to figure out how to access those registers. Anyone come across this before? What space are those actually in (IO, Memory, ??). The register widths are also strange (64 and 16 bits).

Thanks,
Nate

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They are MSRs for Pentium-M found in Centrino platforms, but acpi spec would only say you that you have to contact the CPU vendor.

Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.


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Ah, thank you. That makes sense. How do you decide which platform you are on to determine how to interpret FFixedHW resources? Check the vendor ID string for the ASL? Check CPU or chipset type? It could be that FFixedHW is MSR on x86 but some other thing (EFI) on ia64.

For this particular laptop, should I be looking in the chipset guide or the CPU guide?

-Nate

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No. A FFixedHW is more likely a way to tell ACPI that OS must provide a specific driver for supporting that. It is just that for this really specific case, they are MSRs, but that is only an accident.

CPU. And anyway, you have to consider that actually this piece of asl is buggy, in the sense that a FFixedHW should not be allowed to store informations, or to be more precise, all fields should be 0.

Some (random) examples:

For a Pentium-M (banias):

Processor (CPU, 0x01, 0x00001010, 0x06) {
	/*
	 * 2.0 P-states
	 */
	Name(_PCT, Package() {
		ResourceTemplate() {Register (FFixedHW, 0, 0, 0)},	// perf_ctrl
		ResourceTemplate() {Register (FFixedHW, 0, 0, 0)}	// perf_status
	})
	Name(_PSS, Package() {
		Package() {
			1300,		// Frequency
			26000,		// power dissipation
			500,		// transition latency (always worst case)
			0,		// Bus latency
			0x0d2b,		// ctrl
			0x0d2b		// status
		},
		Package() {
			1200,
			22000,
			500,
			0,
			0x0c29,
			0x0c29
		},
		Package() {
			1000,
			20000,
			500,
			0,
			0x0a25,
			0x0a25
		},
		Package() {
			800,
			16000,
			500,
			0,
			0x0823,
			0x0823
		},
		Package() {
			600,
			12000,
			500,
			0,
			0x0610,
			0x0610
		}
	})
	Method(_PPC, 0, NotSerialized) {
		// Don't care.  This is for a badly designed OS anyway
	}
	/*
	 * 2.0 C-states
	 */
	Name(_CST) {
		4, 
		Package () {
			ResourceTemplate () { Register (FFixedHW, 0, 0, 0) },
			1,		// C state type, read 'like C1'
			1,		// Latency 
			933		// Power consumption
		}, 
		Package () {
			ResourceTemplate () { Register (SystemIO, 8, 0, 0x1014) }, 
			2, 
			1, 
			500
		}, 
		Package () {
			ResourceTemplate () { Register (SystemIO, 8, 0, 0x1015) }, 
			3,		// C state like C3, read need BM checks, etc.
			85, 
			250
		}, 
		Package () {
			ResourceTemplate () { Register (SystemIO, 8, 0, 0x1016) }, 
			3, 
			185, 
			100
		} 
	})
}

For P-states: if, and only if, you know you are on an Pentium-M (Banias), and there is a driver for it, then:

	OSPM decide to go to P-state n: call specific driver.
		banias driver will:
			write _PSS for the field 'ctrl' to MSR 0x199
			read MSR 0x198 and return all OK if this equal _PSS[n].'status', else return KO.

For C-states: there is 4 states, and C1 is a FFixedHW. Perform 'hlt' for that state. That one is (again) not a MSR.

An other example. ICH-2M, and PIII-M:

Processor (CPU, 0x01, 0x00001010, 0x06) {
	/*
	 * 2.0 P-states
	 */
	Name(_PCT, Package() {
		ResourceTemplate() {Register (FFixedHW, 0, 0, 0)},	// perf_ctrl
		ResourceTemplate () {Register (FFixedHW, 0, 0, 0)}	// perf_status
	})
	Name(_PSS, Package() {
		Package() {
			933,		// Frequency
			20000,		// power dissipation
			500,		// transition latency (always worst case)
			0,		// Bus latency
			0,		// ctrl
			0		// status
		},
		Package() {
			1200,
			22000,
			500,
			0,
			1,
			1
		}
	})
	..
}

To perform a transition, and there if there is a driver for it (read: CPU *and* chipset):

	from the 0x1010, calculate the IO register for speedstep (0x1010 + 0x40)
		or directly from the ich2-m (speedstep_register = pciconfig pm_base + 0x50).
	
	disable interrupts,
	Bus Mastring off
	outb _PSS.ctrl to speedstep_register
	Bus mastering on
	re-enable interrupts.
	success if _PSS.status == inb(speedstep_register).

As you can see, for this one, there is a need to disable both interrupts and bus mastering, and therefore you can not just outb to the perf_ctrl.

I can provide more examples, I guess, but this mail is becoming long.

Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.


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